Slide ball joints and bulldozer frame employing same

ABSTRACT

Connection between bulldozer blade and push arm allowing horizontal angle of push arm with respect to bulldozer blade to change during tilting of bulldozer blade. The connection between the front end of each push arm and one end of the bulldozer blade comprises a pin carried by the bulldozer blade, a ball part mounted on the pin for sliding therealong, and a socket part mounted on the front end of the push arm and receiving the ball part in a spherical connection.

United States Patent Deli et al. 1 July 8, 1975 [54] SLIDE BALL JOINTS AND BULLDOZER 3,452,828 7/1969 Deli 172/803 E E 3,656,558 4/1972 Kolinger 172/803 FRAME MPLOYING SAM 3,743,032 7/1973 Schick 172/803 [75] Inventors: Jack M. Deli, Wheaten; William P.

Macarus Palos Park both Of Primary Exam1'nerStephen C. Pellegrino [73] Assignee: International Harvester Company, Arr mey. g Firm-John Gaines; Floyd Chicago, 111. Harman [22] Filed: July 13, 1973 57 [21] Appl. No: 378,847 I 1 ABSTRACT Connection between bulldozer blade and push arm allowing horizontal angle of push arm with respect to [52] US. Cl.2 172/803; 172/803 buudozer blade to change during tilting of bulldozer II."- Cl. blade. The connection between the front end of each Field Of Search p arm and one end of the bulldozer blade prises a pin carried by the bulldozer blade, 21 ball part [56] Refemnces cued mounted on the pin for sliding therealong, and a UNXTED STATES PATENTS socket part mounted on the front end of the push arm 2,827,717 3/l958 Duke et a1. 172/803 and receiving the ball part in a spherical connection. 3,395,764 8/1968 Wirt 172/803 3,441,092 4/1969 Drone 172/803 6 Clams, 3 Drawlng Figures SLIDE BALL JOINTS AND BULLDOZER FRAME EMPLOYING SAME This invention relates to a connection between a bulldozer blade and a push arm. More specifically, the invention relates to a connection of this type providing for stress relief during adjustment of the horizontal angle between a push arm and a bulldozer blade during tilting of the bulldozer blade. The push arm is in effect self-aligning behind the blade, for each of the full tilt and untilted positions of the blade.

In a known construction, a constant angle, for example a right-angle, relationship between push arms and a bulldozer blade is maintained by diagonal struts that are connected to the bulldozer and the push arms in spaced relation to the connections between the front ends of the push arms and the end portions of the bulldozer blade. Hydraulic power units are incorporated in links connecting tops of the ends of the bulldozer with the push arms and adjust the lengths of the links for tilting and pitching the bulldozer blade. During blade tilt, which is accomplished by lengthening of one link through its power unit and shortening of the other link through its power unit, the horizontal angle of each push arm with respect to the bulldozer blade tends to decrease somewhat from 90. This tendency is opposed by the diagonal struts, and consequently great strain is imposed on the push arms and on the connections of the push arms with the tractor that carries the push arms and bulldozer blade.

According to the present invention, a connection between the front end of each push arm and the end portion of the bulldozer blade has been provided which causes the push arm to be at 90 with respect to the bulldozer blade with the help of the diagonal strut, and permits a decrease in this 90 angle during tilting of the bulldozer blade.

More specifically, the bulldozer frame provided ac cording to our invention comprises: a supported blade; push arm means supporting the blade for tilting movement and having push ends on the arm means secured by coaxial joints to the blade; diagonal struts interconnecting first regions of the push arm means and second regions of the blade; the interconnected regions of the push arm means and blade being spaced apart from the joints, and said second regions being jointly on the coaxis of the joints; the push ends being slidably related to the blade at the respective joints for limited coaxial movement, essentially free from bias within the joint; there being ball joint connections between the interconnecting struts and the second regions of the blade, and being jointly with the second regions disposed on the joint coaxis, to accommodate blade pitching on the resulting common axis; the joints each comprising a pin concentric to the coaxis of the joints, a ball socket part, and an interconnecting ball enabling the socket part to twist, to pivot, and to turn relative to the pin; the ball being slidably mounted on the pin, affording the push end-to-blade slidable relationship as described, between the socket part and pin in the joint, when the ball slides; each second region of the blade having freedom to pitch up and down on the pin axis, freedom to slide along the pin axis, freedom to yaw from side to side, and freedom to tilt the pin axis.

In the drawings:

FIG. 1 is a plan view of an assembly of bulldozer blade and push arms, with parts removed;

FIG. 2 is a diagrammatic perspective view of the assembly; and

FIG. 3 is a fragmentary horizontal sectional view of the connection between a push arm and the bulldozer blade,

As shown in H05. 1 and 2, a frame assembly 10 comprising a bulldozer blade 11 and two push arms 12 is mounted on a tractor 13. The front ends of the push arms 12 are connected to end portions of the bulldozer blade I], and rear ends of the push arms 12 are connected to trunnions 14 carried at the sides of the tractor 13 for up and down pivotal movement of the assembly of the bulldozer blade 11 and push arms 12 about a horizontal axis 15.

Connections 16 between the front ends of the push arms 12 and the bulldozer blade 11 are the subject of the present invention. Sometimes known as selfaligning bushing assemblies when applied to other and different purposes, these connections 16 for the purpose of their present novel application will be described in greater detail. The connections 16 provide for a right-angle relationship between the push arms 12 and the bulldozer blade ll during normal operation, and maintenance of this right-angle relationship is aided by diagonal struts 16a whose ends are connected by four ball joints to portions of the bulldozer blade 11 and the push arms 12 spaced apart from the connections 16.

The vertical relationship of the bulldozer blade 11 with the push arms 12 is maintained by adjustable links 17 incorporating power units 18. Each power unit 18 comprises a cylinder 19 and a piston 20 slidably mounted therein. One end of each link 17, or more particularly a rod attached to the piston 20 and protruding from the cylinder 19, has a connection of the ball type with an end portion of the bulldozer 11 near the top thereof. The other end of the link 17, or more particularly a rod-like extension of the cylinder 19, is connected to an intermediate portion of the push arm 12. For pitching of the bulldozer blade 1], both links 17 are lengthened or shortened by adjustment of the pistons 20 in the same direction in the cylinders 19. For tilting of the bulldozer blade 11, one link 17 is length ened, and the other shortened, by shifting of one piston 20 in one direction and the other piston in the other direction. Conventional lift cylinders raise and lower the frame assembly by power.

As shown in FIG 3, each connection 16 comprises a pin 2] carried by the bulldozer blade 11, an annular ball part 22 mounted on the pin 2] so as to be slidable thereon, and a socket part 23 carried by the front end of one push arm 12 and receiving the ball part 22 in a spherical connection. No springs are provided for the connections 16, in which pre-load coil or pre-load torsion springs, useful for slack take-up for example, are not believed necessary or desirable. The pin 21 extends through and is carried by spaced apart lugs 24 secured to the rear face of the bulldozer blade 11 near its end. The pin 21 is held against axial movement in the lugs 24 by a head 25 on the pin engaging the outer side of one lug and by a cotter pin 26 extending through the end of the pin away from the head directly adjacent the outer face of the other lug. The socket part 23 is held against a shoulder formed in an opening in the front end of the push arm 12 by a back-up ring 27, which is secured in place by a retainer ring 28 attached by screws to the front end of the push arm 12. The space between the spaced apart lugs 24 is appreciably larger than the combined width of the push arm and retainer 28, in the vicinity of the retainer 28. Although misleading in its look, the joint nevertheless has the obvious look of looseness or instability in the showing of FIG. 3. Actually, the push ends are drawn in when the blade 11 is horizontal, and are separated when the blade tilts. This geometry is dependent upon proper push arm alignment made during initial installation, as detailed in the closing paragraph of our present application.

The ball part 22 is slidable along the pin 21 and may rotate with, or with respect to, the pin. The spherical connection between the ball part 22 and the socket part 23 permits the push arm angular movement into and out of the plane of the paper in FIG. 3 such as would be required in pitching of the bulldozer blade 1], as well as an angular shift of the push arm 12 in the plane of the paper in FIG. 3 involving a decrease in the horizontal angle of the push arm with the bulldozer blade I]. So overall, the ball on the pin 21 enables the push arm to twist, pivot, turn, and slide relative to the pm.

The geometry of blade tilt will lend background interest to the reader. ln known bulldozer frames, tilting the blade induces bending forces in the push arms, both of which tend to bow outwardly under the strain. The geometry is explained in another specification, US. Pat. No. 3,452,828 owned by the same assignee. Various purposes are served by tilting the blade, such as to lower the blade at one corner in order to get that corner under an obstructing boulder, and loosen and work the boulder out of the ground.

During normal operation of bulldozer blade H, the right-angle relationship between the push arms 12 and the bulldozer 11 is maintained with the aid of the diagonal struts 160. When the bulldozer blade ll is pitched, it swings up or down about the coaxis of the two, athwartwise disposed pins 21, while the push arms stay at right angles to the athwartwise disposed bulldozer, or more particularly, to the athwartwise disposed pins 21.

When, however, the bulldozer blade I1 is tilted by shortening of one link 17 and lengthening of the other, the forces set up tend to decrease the angle of the push arms 12 with the bulldozer blade ll to less than right angles. Such decrease from the right angles can occur, because the front ends of the push arms 12 may move outwardly away from one another, because the ball parts 22 may slide along the pins 2], and the socket parts 23 may move angularly with respect to the ball parts 22 about axes transverse to the pins 21. Consequently, in contrast to behavior in known bulldozer frames, there is no tendency for the push arms 12 according to our invention to bend at the regions where the diagonal struts 16a are connected.

If a side load is applied thereto when the blade 11 is horizontal, its lateral movement transverse to the push arms 12 can occur to a limited extent. Such movement is limited by engagement ofthe lugs 24 on the bulldozer blade 11 with the sides of the ends of the push arms 12 and the retainer rings secured thereto.

Other than for the essentiality of ball type joints carried at each end, the diagonal struts 16a are standard bipartite construction, adjustable to a fixed length by the usual screw threaded connection provided between the end parts of the strut.

The struts are used for alignment purposes during initial installation of the frame made while the blade is horizontal. Preferably, one strut l6a is first foreshortened to take up clearance between the associated narrow push end of the push arm 12 and the medial one of the two lugs 24 concerned. Second, the other strut 16a is foreshortened to a similar extent. in this way, limited lateral travel room is afforded for separation of the narrow push ends, all in the interest of automatic stress relief, rather than the known automatic push arm bending encountered, during subsequent blade tilt. In full tilt, the bulldozer frame is rigid to side loads, because the narrow push arm ends solidly abut the outermost ones of the lugs 24 concerned.

What is claimed is:

1. An assembly comprising a bulldozer blade, push arms having ends adjacent end portions of the bulldozer blade, diagonal struts provided with screw threaded connections between the ends of the struts for individual adjustment of each of same to a fixed strut length, and connecting regions of the push arms and the bulldozer blade spaced from said end portions of the bulldozer blade and said ends of the push arms, means comprising power unit means connecting the push arms with the bulldozer blade for tilting the same, and joints between said ends of the push arms and said end portions of the bulldozer blade accommodating the tendency of the angles between the push arms and the bulldozer blade to change with tilting of the bulldozer blade and the tendency of the diagonal struts to resist such change, each joint comprising a cross pin carried by medial and lateral pin-mounting-means on one of the bulldozer blade and the associated push arm, a ball part encountering predetermined clearance between the associated medial and lateral pin-mounting-means, and mounted on the pin, said ball part capable of predetermined limited movement to slide with respect to the pin between the pin-mounting-means and along the pin access, and a socket part connected to the other of the bulldozer blade and the associated push arm and receiving the ball part in a spherical connection, one of said joints in initial installation with the blade horizontal being without clearance between the associated push arm end and the medial lug, and having said predetermined clearance established between the associated push arm end and the lateral lug, the other joint being similarly without medial clearance and having as lateral clearance said predetermined clearance, all in the interest of automatic stress relief during blade tilt.

2. An assembly comprising a bulldozer blade, a bulldozer, push arms on the bulldozer having front ends for connection to respective end portions of the bulldozer blade, diagonal struts connecting the push arms with the bulldozer blade at regions spaced from the front ends of the push arms and said end portions of the bulldozer blade, means connecting the bulldozer blade and the push arms for tilting the bulldozer blade, and joints between the front ends of the push arm and said end portions of the bulldozer blade for accommodating the tendency of the angles between the push arms and the bulldozer blade to change with tilting of the bulldozer blade and the tendency of the diagonal struts to resist such change, each joint comprising spaced apart, medial and lateral lugs attached to and projecting in the same direction from one of the bulldozer blade and the associated push arm, a ball part, a pivot pin interc0nnecting the ball part and the lugs so as to permit the ball part to rotate with the pivot pin as well as with respect to the pivot pin about its axis, the ball part encountering predetermined limited clearance in the space between the associated medial and lateral lugs, so as to :be capable of predetermined limited, movement, slidably with respect to the pivot pin in a direction along its axis, and a socket part receiving the ball part and attached to the other of the bulldozer blade and the associated push arm, one of said joints in initial installation with the blade horizontal being without clearance between the associated push arm front'end and the medial lug, and having said predetermined c learance established between the associated push arm front end and the lateral lug, the other joint being similarlywithoutmedial clearance and having as lateral clearance said predetermined clearance, all in the interest of automaticstress relief during blade tilt.

3. Bulldozer frame comprising: a supported blade; i push arm means supportingthe blade for tilting movement and having push ends on the arm means secured by coaxial joints to the blade; and diagonal struts interconnecting first regions of the push arm means and second regions of the blade; the interconnected regions of the push arm means and blade being spaced apart from the joints, and said second regions being jointly disposed on the coaxis of said joints; said push ends being slidably related to the blade at the respective joints for limited coaxial movement in the latter, essentially free from bias within the joint; there being ball joint connections between the interconnecting struts and said second regions of the blade, and being jointly with the second regions disposed on the joint coaxis. to accommodate blade pitching on the resulting common axis; each of the coaxial joints characterized by a pin concentric to the coaxis of said joints, a ball socket part, and an interconnecting ball enabling the socket part to twist, to pivot, and to turn relative to the pin; each joint characterized by the ball being slidably mounted on the pin with predetermined clearance provided between medial and lateral pin-mountingmeans, affording the push end-to-blade slidable relationship as described, between the socket part and pin in the joint, when the ball slides; each second region of said blade having freedom to pitch up and down on the pin axis, freedom to slide along the pin axis, freedom to yaw from side to side, and freedom to tilt the pin axis; one of said joints in initial installation with the blade horizontal being without clearance between the associated push end and the medial pin-mountingmeans, and having said predetermined clearance established between the associated push end and lateral pin-mounting-means; the other joint being similarly without clearance and having the predetermined clearance established, all in the interest of automatic stress relief during blade tilt. 4. Bulldozer frame comprising: a supported blade; push arm means supporting the blade for tilting movement and having push ends on the arm means secured by coaxial joints to the blade; and diagonal struts interconnecting first regions of the push arm means and second regions of the blade;

the interconnected regions of the push arm means and blade being spaced apart on the joints, and said second regions being jointly disposed on the coaxis of said joints;

' said push ends being slidably related to the blade at the respective joints for limited coaxial movement in the latter, essentially free from bias within the joint; i

" there being ball joint connections between the intereach joint further characterized by the ball being slidably mounted on the pin with predetermined clearance provided between medial and lateral pinmounting-means, affording the push end-to-blade slidable relationship as described, between the socket part and pin in the joint, when the ball slides;

each second region of said blade having freedom to pitch up and down on the pin axis, freedom to slide along the pin axis, freedom to yaw from side to side, and freedom to tilt the pin axis;

one of said joints in initial installation with the blade horizontal being without clearance between the associated push end and the medial pin-mountingmeans, and having said predetermined clearance established between the associated push end and lateral pin mounting means;

the other joint being similarly without clearance and having the predetermined clearance established, all in the interest of automatic stress relief during blade tilt; and

power means between the frame and blade to pitch and tilt the blade.

5. Bulldozer frame comprising:

a supported blade;

supporting push arm means supporting the blade for tilting movement and having push ends on the arm means secured by coaxial joints to opposite ends of the blade; and

diagonal struts provided with screw threaded connections between the ends of the struts for individual adjustment of same to a fixed strut length, and interconnecting first regions of the push arm means and second regions of the blade;

the interconnected regions of the push arm means and blade being spaced apart from the joints, and said second regions being jointly disposed on the coaxis of said joint;

said push ends being slidably related to the blade at the respective joints for predetermined limited coaxial movement in the latter, essentially free from bias within the joint;

there being ball joint connections between the interconnecting struts and said second regions of the blade, and being jointly with the second regions disposed on the joint coaxis;

each of the joints characterized by:

widely spaced apart medial and lateral lugs on the blade end concerned, a mounting ball socketed in the push arm end concerned, and a pin through the ball extending lengthwise to the length of the blade and carried in the wide space between, and carried by, the lugs, said push arm mounting ball turning and sliding on the pin;

one joint in initial installation with the blade horizontal having the clearance taken out between the associated push end and the medial one of the lugs concerned;

the other joint having the clearance similarly taken out, whereby limited lateral travel room is afforded for separation of the push ends, all in the interest of automatic stress relief during blade tilt.

6. ln initial installation in a bulldozer of a horizontally installed lengthwise supported blade. supporting push arm means therefor supporting the blade for tilting movement, and having push ends on the arm means each slidably secured. by widely spaced apart medial and lateral, pin carrying lugs on the blade and a lengthwise extending pin through each of said push ends, to the length of the blade, each pinned push end confined to a locus of points in the space between an associated medial lug and lateral lug, and diagonal struts disposed one interconnecting each end of the lengthwise supported blade and the associated push arm end at that end of the blade, each strut adjustable, for changing its effective length, by being foreshortenable between its ends. a frame alignment method characterized by the steps of:

foreshortening one strut to take up the clearance between the associated push end and the medial one of the lugs concerned, and foreshortening the other strut similarly to take up the clearance, whereby limited lateral travel room is afforded for separation of the push ends, all in the interest of automatic stress relief during blade tilt. 

1. An assembly comprising a bulldozer blade, push arms having ends adjacent end portions of the bulldozer blade, diagonal struts provided with screw threaded connections between the ends of the struts for individual adjustment of each of same to a fixed strut length, and connecting regions of the push arms and the bulldozer blade spaced from said end portions of the bulldozer blade and said ends of the push arms, means comprising power unit means connecting the push arms with the bulldozer blade for tilting the same, and joints between said ends of the push arms and said end portions of the bulldozer blade accommodating the tendency of the angles between the push arms and the bulldozer blade to change with tilting of the bulldozer blade and the tendency of the diagonal struts to resist such change, each joint comprising a cross pin carried by medial and lateral pin-mounting-means on one of the bulldozer blade and the associated push arm, a ball part encountering predetermined clearance between the associated medial and lateral pin-mountingmeans, and mounted on the pin, said ball part capable of predetermined limited movement to slide with respect to the pin between the pin-mounting-means and along the pin access, and a socket part connected to the other of the bulldozer blade and the associated push arm and receiving the ball part in a spherical connection, one of said joints in initial installation with the blade horizontal being without clearance between the associated push arm end and the medial lug, and having said predetermined clearance established between the associated push arm end and the lateral lug, the other joint being similarly without medial clearance and having as lateral clearance said predetermined clearance, all in the interest of automatic stress relief during blade tilt.
 2. An assembly comprising a bulldozer blade, a bulldozer, push arms on the bulldozer having front ends for connection to respective end portions of the bulldozer blade, diagonal struts connecting the push arms with the bulldozer blade at regions spaced from the front ends of the push arms and said end portions of the bulldozer blade, means connecting the bulldozer blade and the push arms for tilting the bulldozer blade, and joints between the front ends of the push arm and said end portions of the bulldozer blade for accommodating the tendency of the angles between the push arms and the bulldozer blade to change with tilting of the bulldozer blade and the tendency of the diagonal struts to resist such change, each joint comprising spaced apart, medial and lateral lugs attached to and projecting in the same direction from one of the bulldozer blade and the associated push arm, a ball part, a pivot pin interconnecting the ball part and the lugs so as to permit the ball part to rotate with the pivot pin as well as with respect to the pivot pin about its axis, the ball part encountering predetermined limited clearance in the space between the associated medial and lateral lugs, so as to be capable of predetermined limited movement, slidably with respect to the pivot pin in a direction along its axis, and a socket part receiving the ball part and attached to the other of the bulldozer blade and the associated push arm, one of said joints in initial installation with the blade horizontal being without clearance between the associated push arm front end and the medial lug, and having said predetermined clearance established between the associated push arm front end and the lateral lug, the other joint being similarly without medial clearance and having as lateral clearance said predetermined clearance, all in the interest of automatic stress relief during blade tilt.
 3. Bulldozer frame comprising: a supported blade; push arm means supporting the blade for tilting movement and having push ends on the arm means secured by coaxial joints to the blade; and diagonal struts interconnecting first regions of the push arm means and second regions of the blade; the interconnected regions of the push arm means and blade being spaced apart from the joints, and said second regions being jointly disposed on the coaxis of said joints; said push ends being slidably related to the blade at the respective joints for limited coaxial movement in the latter, essentially free from bias within the joint; there being ball joint connections between the interconnecting struts and said second regions of the blade, and being jointly with the second regions disposed on the joint coaxis, to accommodate blade pitching on the resulting common axis; each of the coaxial joints characterized by a pin concentric to the coaxis of said joints, a ball socket part, and an interconnecting ball enabling the socket part to twist, to pivot, and to turn relative to the pin; each joint characterized by the ball being slidably mounted on the pin with predetermined clearance provided between medial and lateral pin-mounting-means, affording the push end-to-blade slidable relationship as described, between the socket part and pin in the joint, when the ball slides; each second region of said blade having freedom to pitch up and down on the pin axis, freedom to slide along the pin axis, freedom to yaw from side to side, and freedom to tilt the pin axis; one of said joints in initial installation with the blade horizontal being without clearance between the associated push end and the medial pin-mounting-means, and having said predetermined clearance established between the associated push end and lateral pin-mounting-means; the other joint being similarly without clearance and having the predetermined clearance established, all in the interest of automatic stress relief during blade tilt.
 4. Bulldozer frame comprising: a supported blade; push arm means supporting the blade for tilting movement and having push ends on the arm means secured by coaxial joints to the blade; and diagonal struts interconnecting first regions of the push arm means and second regions of the blade; the interconnected regions of the push arm means and blade being spaced apart on the joints, and said second regions being jointly disposed on the coaxis of said joints; said push ends being slidably related to the blade at the respective joints for limited coaxial movement in the latter, essentially free from bias within the joint; there being ball joint connections between the interconnecting struts and said second regions of the blade, and being jointly with the second regions disposed on the joint coaxis, to accommodate blade pitching on the resulting common axis; each of the coaxial joints characterized by a pin concentric to the coaxis of said joints, a ball socket part, and an interconnecting ball enabling the socket part to twist, to pivot, and to turn relative to the pin; each joint further characterized by the ball being slidably mounted on the pin with predetermined clearance provided between medial and lateral pin-mounting-means, affording the push end-to-blade slidable relationship as described, between the socket part and pin in the joint, when the ball slides; each second region of said blade having freedom to pitch up and down on the pin axis, freedom to slide along the pin axis, freedom to yaw from side to side, and freedom to tilt the pin axis; one of said joints in initial installation with the blade horizontal being without clearance between the associated push end and the medial pin-mounting-means, and having said predetermined clearance established between the associated push end and lateral pin mounting means; the other joint being similarly without clearance and having the predetermined clearance established, all in the interest of automatic stress relief during blade tilt; and power means between the frame and blade to pitch and tilt the blade.
 5. Bulldozer fRame comprising: a supported blade; supporting push arm means supporting the blade for tilting movement and having push ends on the arm means secured by coaxial joints to opposite ends of the blade; and diagonal struts provided with screw threaded connections between the ends of the struts for individual adjustment of same to a fixed strut length, and interconnecting first regions of the push arm means and second regions of the blade; the interconnected regions of the push arm means and blade being spaced apart from the joints, and said second regions being jointly disposed on the coaxis of said joint; said push ends being slidably related to the blade at the respective joints for predetermined limited coaxial movement in the latter, essentially free from bias within the joint; there being ball joint connections between the interconnecting struts and said second regions of the blade, and being jointly with the second regions disposed on the joint coaxis; each of the joints characterized by: widely spaced apart medial and lateral lugs on the blade end concerned, a mounting ball socketed in the push arm end concerned, and a pin through the ball extending lengthwise to the length of the blade and carried in the wide space between, and carried by, the lugs, said push arm mounting ball turning and sliding on the pin; one joint in initial installation with the blade horizontal having the clearance taken out between the associated push end and the medial one of the lugs concerned; the other joint having the clearance similarly taken out, whereby limited lateral travel room is afforded for separation of the push ends, all in the interest of automatic stress relief during blade tilt.
 6. In initial installation in a bulldozer of a horizontally installed lengthwise supported blade, supporting push arm means therefor supporting the blade for tilting movement, and having push ends on the arm means each slidably secured, by widely spaced apart medial and lateral, pin carrying lugs on the blade and a lengthwise extending pin through each of said push ends, to the length of the blade, each pinned push end confined to a locus of points in the space between an associated medial lug and lateral lug, and diagonal struts disposed one interconnecting each end of the lengthwise supported blade and the associated push arm end at that end of the blade, each strut adjustable, for changing its effective length, by being foreshortenable between its ends, a frame alignment method characterized by the steps of: foreshortening one strut to take up the clearance between the associated push end and the medial one of the lugs concerned; and foreshortening the other strut similarly to take up the clearance, whereby limited lateral travel room is afforded for separation of the push ends, all in the interest of automatic stress relief during blade tilt. 